1. Field of the Invention
The invention relates to the sensing of an object, such as foliage, using laser optics. A size of the foliage is determined for controlling the amount of a selected spray material needed to be directed at the foliage for an appropriate agricultural spraying application.
2. Background Art
The spraying of chemicals on plants for nutritional, disease and pest control purposes is a vital factor in maintaining the high level of productivity which has come to characterize the agricultural art. With this spraying comes concern about pollution of our environment, particularly our water supply. There are thus environmental as well as an economic incentives for optimizing the chemical spraying process so that the greatest agricultural benefit is achieved with the least damage to the environment. Optimization of the spraying process continues as new technology becomes available. This is aptly illustrated by the evolution of mobile agricultural sprayers used for spraying trees in groves and orchards.
Early grove sprayers employed pressurized nozzles at the end of a wand which an operator moved around so as to direct the spray over the entire canopy of a tree. In a subsequent improvement, several wands were attached to a pipe mounted to a swivel at the rear of a pump/tank trailer. The operator set the elevation angles of the wands according to tree size and swiveled the entire assembly back and forth to facilitate spray penetration of the foliage. By varying the nozzle pressure and orifice size, the operator controlled the flow rate, droplet size, and the force of the flow stream. The operator had to estimate the size of the tree and how long to apply spray to achieve appropriate coverage. The operator could turn off the spray between trees by means of valves to each wand. These early sprayers were cumbersome and time consuming to use.
The development of the air-blast sprayer as disclosed in the U.S. Pat. No. 2,475,449 issued to G. W. Daugherty on Jul. 5, 1949, "Spraying Machine," improved sprayer effectiveness by removing the operator from the spray zone, approximately doubling the acreage sprayed per day and providing a more thorough spray coverage of foliage. The air-blast sprayer used large volumes of high speed air at approximately 100 miles per hour (mph) to propel the droplets ejected from pressurized nozzles. Swirl plates beneath the nozzle orifices were used to enhance the backup of droplets as they entered the air stream. The spray vehicle moved at approximately 0.5 mph to 1.5 mph between rows of trees, spraying the trees on either side at a typical spray material application rate of approximately 500 to 1500 gallons of chemical/water mix per acre. The air-blast sprayers were not turned off between trees or at gaps where trees were missing or where short replants were located.
Although the air-blast sprayer was an improvement over previous devices, its use of highly diluted solutions had undesirable consequences. There was a substantial loss of chemicals from foliage due to runoff which deposited the chemicals in the soil, thereby degrading its fertility. In addition, the use of large amounts of water required large and heavy equipment which led to high fuel consumption.
The use of concentrated solutions in sprayers requires uniform spray distribution and accurate spray metering to avoid the chemical waste and possible vegetation damage occurring from chemical over-concentrations and to avoid the ineffectiveness of the spray function resulting from under-concentrations. U.S. Pat. No. 3,489,351 issued to J. M. Patterson on Jan. 13, 1970, "High Concentrate Sprayer," discloses modifications to the air-blast sprayer design to provide accurate spray metering and uniform spray distribution. Two blowers in a vertical stack are employed having axial inlets and radial outlets ducted together to blend the flows into a uniform speed air blast from the top to the bottom of the tree being sprayed. Accurate spray metering is achieved using a proportional ground speed pump drive and proportioning ceramic orifices. Typical application rates from 100 to 250 gallons of water/chemical per acre were achieved.
U.S. Pat. No. 4,768,713 issued to B. E. Roper on Sep. 6, 1988, "Grove Sprayer," discloses the use of an ultrasonic sonar-type sensor to detect the presence of tree foliage as a spray vehicle traveled through the grove. Multiple spray nozzles and a plurality of associated foliage sensors are positioned at elevation angles such that spray coverage is divided into several zones corresponding to the expected variations in tree height. Foliage is then permitted only in the zones where foliage is detected. Using special nozzles in a high-speed air blast of approximately 200 mph and a water/chemical feed rate proportional to ground speed along with zone spraying achieves an effective spraying process. Typical application rates of one to ten gallons per acre are achieved. By traveling at sprayer travel speeds of approximately 10 mph, 150 acres per day can be sprayed. Beyond this increased productivity, the use of the ultrasonic sonar-type sensor has reduced water, chemical and fuel usage and greatly reduces soil and water pollution.
U.S. Pat. No. 4,823,268 issued to Durham K. Giles et al. on Apr. 18, 1989, "Method and Apparatus for Target Plant Foliage Sensing and Mapping and Related Materials Application Control," discloses an electronic orchard tree measuring system based on the use of a plurality of ultrasonic range transducers for determining the amount and vertical distribution of sensed load centroids in vertical sectors of orchard trees. The ultrasonic transducers may be operated independently of any processor or memory which receives their distance data outputs. Displacement sensing of the apparatus relative to a row of target trees may instead be used to select ultrasonic distance data at predetermined incremental distances of travel relative the trees being sensed. Thus, the most recent value of sensed data is always available as input to the processor or memory without requiring any timing circuitry between such sensing and control circuits. The detection may be stored in memory for subsequent processing to create a map of foliage volumes of the sensed target trees. Alternatively, the spatial characteristics of the sensed amount and vertical distribution of load centroids for a given vertical segment of target trees may be further compared spatially with determined application patterns of controllable spray nozzles to configure subsequent activation of such nozzles for optimal material application to the given vertical segment of the sensed target trees.
U.S. Pat. No. 5,172,861 issued to Lenhardt on Dec. 22, 1992 discloses an agricultural sprayer comprising an oscillating sensor that detects the foliage location and turns nozzles off and on to spray different foliage locations. The sensor includes an ultrasonic device for directing a beam of ultrasonic energy towards a selected target and sensing the reflection of ultrasonic energy off that target. The sensor has a horn for further directing the ultrasonic sound in the direction of a predetermined spraying zone. A stepper motor rotates the horn of the foliage sensor into various orientations where the foliage is sampled. A distance signal is sent to a computer system which determines if the distance in a sampled zone is within a predetermined range. After determining the range of the distance signals, the computer system enables solenoids to spray zones having distance signals in the predetermined range. If the computer determines that the sensed foliage in a zone is outside the predetermined range, the solenoids for that spray zone are disabled. The disclosure recognizes the need and value in having a single sensor in the sprayer control system.
The object sensor were developed by the inventors as an outgrowth of several laser systems developed for Department of Defense programs. Typically military use of laser optics and electronics is in missile systems and target recognition systems. Target images are produced and are seen as a missile or carrier flies over a targeting area. For example, a missile may be equipped with a laser range finder scanning in a plane perpendicular to the flight path. Range-image sensors have been developed which employ two mirrors having orthogonal axes of rotation t scan a diode-laser rang finder in elevation and azimuth. This provides angle-angle-range data from which three dimensional images have been constructed. The ranging and imaging capabilities of this type of sensor are well suited for submunition target recognition and identification applications.
Optical dimensioning techniques have been incorporated in industrial uses as disclosed in U.S. Pat. No. 4,179,216 issued to Josef Theurer and Klaus Riessberger on Dec. 18, 1979, "Apparatus for Measuring the Profile of a Railroad Tunnel." In this patent, a mobile apparatus for measuring the profile of a railroad tunnel comprising a car mounted for mobility on the railroad track, a beam emitter and receiver instrument capable of continuously receiving a signal corresponding to the distance of the tunnel profile from the instrument, a rotatable axle supporting the instrument on the car for pivoting about an axis extending parallel to the longitudinal track axis, and a drive arranged to pivot the instrument about the axis extending parallel the track axis whereby the instrument may sweep the profiler and continuously receive the signal. The same inventors disclose a similar use for the sensor in their U.S. Pat. No. 4,490,038 issued on Dec. 25, 1984, "Mobile Apparatus for Determining the Lateral Position of a Railroad Track." In this patent the laser beam emitting and receiving instrument is focused for measurement of the distance to an adjacent railroad track.